The invention relates to a method for carrying out endothermic or exothermic gas phase reactions by using a tube bundle reactor with a tube bundle of reaction tubes filled with a catalyst, the method comprising the following steps: Introducing a reaction gas mixture into the reaction tubes; dividing the reaction gas mixture flow flowing through each of the reaction tubes into at least two partial flows, the partial flows having the same composition; feeding each partial flow at a different point along the catalyst filling thereinto with an existing flow resistance.
The invention also relates to a tube bundle reactor for use with such a method, the tube bundle reactor comprising a tube bundle of catalyst-filled reaction tubes, the one ends of which are spanned by a gas inlet hood and the other ends by a gas outlet hood and through which a reaction gas mixture flows and which have a respective feeder device that is at least partially embedded in the catalyst filling and that divides the reaction gas mixture flow flowing through the reaction tube into at least two partial flows, the partial flows having the same composition and being fed at different points along the catalyst filling thereinto with an existing flow resistance.
Such a tube bundle reactor with which the method cited above is achieved is known from U.S. Pat. No. 3,268,299. With these prior art tube bundle reactors, in each reaction tube a feeder tube is centrically located, that extends from the gas inlet end of the reaction tube into the catalyst filling up through to the latter's end at maximum. Along the entire length of the feeder tubes, gas outlet orifices in the tube wall are distributed at even or uneven intervals through which the reaction gas exits into the catalyst filling. Various geometric shapes are proposed for such gas outlet orifices that could also extend into each other in a continuous slot. In one embodiment the gas inlet ends of the reaction tubes are sealed radially outside of the feeder tubes so that all of the reaction gas flow entering each reaction tube is first led into the feeder tube. With this embodiment a reaction gas mixture is fed into the reaction tubes. With a second embodiment a reaction gas can enter into the reaction tube alongside the feeder tube as well. With the latter embodiment two reactants are fed into the reaction tube separately, the first reactant being fed in via the feeder tube and the second reactant being fed in directly to the catalyst filling alongside the feeder tube.
These known feeder tubes are intended to have a large pressure drop across the gas outlet orifices in comparison to the pressure drop in the longitudinal direction of the feeder tube. This means that the friction pressure drop in the feeder tube should be relatively small, that is the pressure being present in the feeder tube should be approximately constant. This should then provide even outflow along the gas outlet orifices of the feeder tube, mainly in order to avoid or minimise the formation of so-called hot spots in the catalyst filling. In addition the useful life of the catalyst should be prolonged, the through-flow increased and operational safety as well as production rates improved.
From WO 01/85330 A2 it is likewise known to arrange feeder tubes in reaction tubes. In these known feeder tubes, along their longitudinal extent throttles are provided at specified points and are formed as longitudinal bores in the inside of the feeder tube and as gas outlet orifices in the wall of the feeder tube. Via the feeder tube a first reactant is introduced into the catalyst filling while a second reactant is directly introduced into the catalyst filling alongside the feeder tube. This is supposed to avoid the danger of explosion that would otherwise result from joining the two reactants. By means of graduated feeding in of the first reactant, the reactant concentrations in the reaction gas mixture remain below the explosion limit. Introduction of a ready-mixed or ready-made reaction gas mixture into the feeder tube and/or the reaction tube is not provided for in the tube bundle reactor known from WO 01/85330 A2.
An essential problem-with all gas phase reactions is that, besides the intended product (hereinafter referred to simply as “product”), by-products are produced that form because of less than optimum conduct of the reaction, which results in, among other things, unintended subsequent reactions. The portion of by-products with methods and tube bundle reactors where a ready-made reaction gas mixture is fed into reaction tubes to effect endothermic or exothermic gas phase reactions is, regardless of whether or not the reaction tubes contain feeder devices or not, relatively great.